Dialysis is a process for removing waste and excess water from the blood, and is used primarily to provide an artificial replacement for lost kidney function in people with renal failure. Dialysis acts as a substitute for the function which the kidneys normally perform in the body, namely regulating the body's fluid balance and removing waste products which accumulate in the body. A patient generally requires dialysis when his body builds up a level of a waste to such a degree that it causes physical illness.
There are two main types of dialysis: hemodialysis and peritoneal dialysis. Hemodialysis uses a special type of filter to remove excess waste products and water from the body. A double lumen catheter is inserted into the patient's chest or neck into a vein. During hemodialysis, the blood is allowed to slowly flow into the catheter and through the filter, called a dialysis membrane, thereby removing any unwanted products or fluids. A solution within the dialysis machine will capture the removed waste products. Once filtered, the clean blood is returned to the body.
Peritoneal dialysis, on the other hand, uses the patient's own body tissues (the peritoneal membrane) inside of the abdominal cavity to act as the filter, rather than using a machine-like filter. Peritoneal dialysis uses a soft tube called a peritoneal catheter to fill the abdomen with a cleansing dialysis solution liquid, called dialysate. The walls of the abdominal cavity and internal viscera are lined with a membrane, called the peritoneum, which acts as dialysis membrane. The peritoneal membrane separates two fluid-containing compartments—(a) the blood in the peritoneal capillaries, which in kidney failure patients accumulates waste products such as urea, creatinine, potassium etc.; and (b) and the dialysis solution. The peritoneal membrane allows waste products and extra fluid to pass from the blood into the dialysis solution by process of diffusion and ultrafiltration occurring simultaneously. The dialysis solution is then drained from the abdomen, and takes with it the waste products (the solute) which were previously cleared therein. The process of introducing the dialysis solution into the body and removing the excess of fluids (water) and solute is called an exchange, and the period of time in which the dialysis solution is in the abdomen is called the dwell.
Peritoneal dialysis affords patients greater independence and flexibility in their dialysis schedules and location, while its simplicity, safety profile and cost-effectiveness, when compared to home hemodialysis, make it an ideal dialysis modality, especially for younger, working patients. Major obstacles of peritoneal dialysis, however, include catheter-related complications, loss of efficiency of the peritoneal membrane over time, and long hours of dialysis; this invention seeks to address and minimize these obstacles.
Over the last several years, automated peritoneal dialysis (APD) has emerged as the preferred modality of peritoneal dialysis amongst patients and healthcare providers. In automated peritoneal dialysis, the above-mentioned process occurs using a small and lightweight cycler machine while an individual is sleeping. In the United States, two types of automated peritoneal dialysis devices or methods are employed—continuous cycling peritoneal dialysis (CCPD) or nocturnal intermittent peritoneal dialysis (NIPD). CCPD uses an automated cycler to perform multiple exchanges of fluid during the night while the patient sleeps, and then leaves the dialysis solution in the abdomen for the patient to have one more exchange take place which lasts the entire day. NIPD, alternatively, makes more exchanges during the night, and does not require the final exchange during the day.
Another technique is known as Tidal Peritoneal Dialysis (TPD), which provides a high-dialysate flow rate and consequently an increased diffusion gradient between the blood and the dialysate. This minimizes the formation of unstirred layers of dialysate. Continuous contact between the dialysate and peritoneal membrane also provides continuous removal of solute and water, not just intermittent removal during the dwell period. Finally, in some European countries, Continuous Flow Peritoneal dialysis (CFPD) is also used, especially for patients with limited efficiency in standard CAPD (continuous ambulatory peritoneal dialysis) or APD (automated peritoneal dialysis). CFPD provides a continuous movement of dialysate into and out of the abdomen.
Regardless of the technique employed for peritoneal dialysis, all current peritoneal access devices or peritoneal catheters have several typical disadvantages and complications. These common complications include peri-catheter leaks and outflow failure caused by a diminished volume of fluid in the peritoneal cavity. These occur frequently, particularly in the latter stages of the fluid drain, when resistance to fluid outflow increases, and when the bowel loops move closer to the standard catheter tip and side holes, thus causing blockages and preventing the free movement of dialysate in and out of the catheter.
Another limitation in current peritoneal dialysis devices is an inefficient use of the peritoneal membrane surface area. Peritoneal membranes have a surface area of approximately 1,200 square centimeters per square meter of body surface area, or 2,200 square centimeters in an average adult. In current clinical applications of peritoneal dialysis, however, only limited parts of the surface area are seemingly utilized during the procedure. The surface area which is actually contacted during dialysis depends on the position of the catheter and patient. The position of the catheter, if bunched up or blocked in any way such as in an adhesion formation, can cause dialysate fluid to be trapped in pockets that do not participate in the fluid exchange. These issues result in a lengthier period of time required for the removal of all waste from the system, and costs increase as greater amounts of dialysate are required to complete the procedure. This could also result in excess dialysate being trapped in the abdomen.
Another major problem with current peritoneal dialysis is infection. Because of the nature of the machinery used for the procedure, a plastic tube runs from inside the peritoneal cavity to the outside of the body. This creates the potential for bacteria to enter the body, especially if the tubes are not cleaned or used properly.
An additional limitation to current dialysis methods is time. Hemodialysis requires minimal participation by the patient during treatment but requires the patients adhere to very specific schedules and diets. Peritoneal dialysis allows for more flexible scheduling, but requires many hours of dialysis each day and must be done every day of the week. The process of filling the abdomen with dialysis solution, allowing it to mix with the unwanted waste in the body, and then draining the mixture, takes a lengthy period of time. A typical dialysis schedule requires multiple cycles daily, each taking approximately 4 to 6 hours.
The present invention discloses a new and novel peritoneal dialysis catheter. The present invention comprises two silicone shafts, which are each preferably 32 cm long. Each has preferably an inner diameter of 2.5 mm and an outer diameter of 3.5 mm, although the use of alternate dimensions for the catheter is envisioned as well. The first shaft is called the inflow shaft. The terminal 15 cm of the shaft bifurcates into two separate inflow shafts. The second shaft is the outflow shaft, which preferably trifurcates into three or more, smaller outflow shafts. These preferably five shafts are encased in a sheath, which is used to hold the plurality of shafts in place during implantation of all shafts into the peritoneal membrane.
After intra-peritoneal implantation of the catheter, the outer sheath surrounding the shafts is retracted and pulled out. This will have the effect of separating and deploying the plurality of shafts. All shafts take the shape of a basket or shafts forming the outside of an elongated football or some other rounded structure. Each of the shafts contains numerous side perforations of preferably 0.5 mm or smaller. For the ease of implantation, the shafts are preferably joined together at an end, which allows the easiest access of the tubes into the abdomen or peritoneal cavity of a patient, and requires the smallest possible aperture through which to do so.
The middle portion of the catheter has an inflow tube and an outflow tube. These tubes are preferably appended to two Dacron cuffs that are preferably 7 cm apart. A Dacron cuff is a sheath of synthetic fabric which surrounds the inflow and outflow tubes of the catheter to prevent accidental displacement of the tubes. One Dacron cuff is preferably placed on the tubing at the skin level, while the other is preferably placed around the tubing at the peritoneal level. The Dacron felt cuffs are used to create a biological barrier against bacterial invasion at the interface between implanted foreign synthetic materials, i.e. silicone tubes, and the skin. After implantation of peritoneal catheter, body tissues grow into the Dacron felt cuff, thus stabilizing the catheter and forming a biological barrier against infection. The second cuff is located just outside the peritoneal cavity, thus closing the sinus tract at that level. The growth of fibroblasts and tissues into the meshwork of Dacron cuffs not only fixes the catheter in place and prevents sliding, but also provides an efficient barrier against bacterial invasion. By 10-14 days after implantation, tissue ingrowth into the cuffs is virtually complete throughout its thickness.
The initial, or extra-abdominal, portion of the catheter that runs outside of the skin simply provides a means for connecting the inflow and outflow shafts to the peritoneal dialysis apparatus. This portion of the tubing preferably contains a single inflow tube and a single outflow tube for movement of the dialysis solution in and out of the peritoneal membrane. Therefore, in the preferred embodiment of the present invention, all dialysate which enters the inflow tube from the dialysis machine will travel through a single inflow tube until entering the peritoneal cavity, at which point it will disperse into the plurality of inflow tubes to maximize the surface area of the membrane. Then, preferably, the dialysate fluid, along with waste products and excess body water (ultrafiltration), is collected to exit the peritoneal membrane. It will enter into a plurality of the outflow tubes, which will all converge into a single outflow tube upon exit from the abdomen, such that the fluid will travel back to a drainage bag.
Implantation of the present invention is made using open surgical technique or standard laparoscopic methodology, depending on the surgeon's interest and expertise. The laparoscopic technique is becoming more popular because of its advantages in direct visualization of the catheter placement and also in the ability to perform a partial omentectomy or lysis of adhesions during the catheter placement. In the laparoscopic technique, a patient is operated on under general anesthesia. A small incision is made in the abdomen for placement of the catheter, and a tunnel is created into the patient's peritoneal cavity. The invention, multiple shafts or tubes held together by a sheath, is then inserted through the tunnel and into the cavity. After implantation, the surrounding sheath will be retracted from the tubing, thereby leaving behind a basket-shaped system of auxiliary inflow and outflow shafts in the intra-peritoneal cavity. The catheter is placed under direct vision to ensure proper positioning. An internal Dacron cuff is placed in the pre-peritoneal space. Using resorbable sutures, which prevent obstruction of the catheter dialysate leakage, the surgeon closes the peritoneum and rectus sheaths. Subsequently a tunnel is created under the abdominal wall skin, and a distal or external Dacron cuff is placed under the skin at the catheter exit site. The catheter is tested before closing the incision.
This is the crux of the present invention as it differs from all prior dialysis catheters, which comprise merely a single tube for both inflow and outflow of dialysate. Compared to a single tube or single coiled tube peritoneal dialysis catheter (which is the standard catheter used in the field presently), the present inventive catheter device will occupy a larger surface area of the peritoneal cavity and allow for smaller pockets of the peritoneal cavity to participate in peritoneal dialysate exchange with blood capillaries. This not only acts to improve the efficiency of the peritoneum as a dialysis membrane, but it also reduces future pocket formations within the peritoneal membrane by adhesions and other bodily organs such bowel loops. Such pocket formations often occur after a patient suffers from episodes of peritonitis, or inflammation or irritation of the peritoneum.
Due to the basket-shape of the present invention after implantation, the chances of catheter kinking, or curling in on itself, or omentum wrapping are negligible compared to a single tube straight or coiled catheter. In traditional peritoneal dialysis, a single catheter is used which frequently has the complication of dialysate out flow failure, where dialysate may be infused into the peritoneal cavity but where the fluid fails to drain out. The outflow failure usually occurs when omentum or bowel loops move closer to traditional catheters and block the catheter tip and side perforations, thereby blocking free drainage of dialysate through these perforations. Outflow failure can also be caused by other means, including the attachment of omentum or other tissues to a single tube or curled catheter tip and side perforations, the migration of single tube traditional catheters (which increases the chance of attachment to omentum), and diminished volume of the fluid in peritoneal cavity during exchange (which inhibits the free flow of dialysate in and out of the catheter and allows for a blockage of inflow or outflow tubes). The present invention overcomes this problem of catheter migration or omentum attachment, as the basket-shaped catheter uses its own three-dimensional structure to push bowel loops and omentum out of the way of the perforations in the tubes for the inflow and outflow of dialysate.
Another advantage of the present invention is the continuous, simultaneous inflow and outflow of fluid. Due to such movement of dialysate, a pressure gradient will be created between the peritoneal fluid volume and the outflow tubes, allowing for free drainage of the fluid and for minimization of the risk of outflow failure. The plurality of inflow and outflow tubes allow the dialysate to enter the peritoneal cavity, and the waste or unwanted fluid mix to exit the peritoneal cavity, at a much more rapid pace than in a traditional peritoneal dialysis system using a single tube. This provides the advantage of drastically reducing the dwell time needed, since the exchange of the fluids is occurring at a much quicker pace and covering a much greater surface area of the membrane. The purpose of the lengthy period of the dwell in traditional peritoneal dialysis is to allow the entire peritoneal membrane to come in contact with the dialysate, thus removing the unwanted waste (solute) and fluids by diffusion and ultrafiltration. In the present invention, substantially the maximum peritoneal surface area and peritoneal capillaries participate in peritoneal transport and therefore the exchange is performed efficiently at a much quicker pace.
Additionally, a multitude of points within the cavity are directly targeted by individual inflow tubes, so there is a limited wait for the dialysate to cover the entire surface area of the membrane. Likewise, a multitude of outflow tubes exist to remove the unwanted solute, ultrafiltered water, and used dialysate from the abdomen upon completion of the dwell. Both of these advantages substantially reduce the time requirement for the dialysis procedure, while also minimizing the recirculation of the same fluid which has already undergone the exchange, thereby improving dialysis clearance. Low dialysis clearance is a frequent problem in dialysis when a single tube or coiled catheter becomes lodged in a peritoneal pocket. Using the present invention, the dialysis procedure can be done efficiently and at a much quicker pace, thereby allowing an individual requiring dialysis multiple times a day greater flexibility in his schedule, while simultaneously obtaining a superior result.